Merge pull request #5 from dynata-bradley/feature/add-authentication

some documentation for POP-2271, POP-2272 & POP-2273

Author: DynataRidley

.env-example

@@ -0,0 +1,3 @@
+DYNATA_DEMAND_CLIENT_ID=
+DYNATA_DEMAND_USERNAME=
+DYNATA_DEMAND_PASSWORD=

README.md

@@ -1,5 +1,20 @@
 # python-demandapi-client
 A Python client library for the Dynata Demand API
 
-# Testing
+## Setup
+
+The client requires environment variables to be set for the Dynata Demand API credentials. These can be found in `.env-example`.
+
+## Example Usage
+
+    demandapi = DemandAPIClient()
+    demandapi.authenticate()
+    demandapi.logout()
+
+## Contributing
+
+Information on [contributing](CONTRIBUTING.md).
+
+## Testing
+
 Use the command `pytest tests` to run the tests for this project.